Conventional methods of oil recovery do not exploit anywhere near all of the oil enclosed in reservoir rock. Many types of enhanced oil recovery methods are used to enhance extraction—including gas, liquid or steam flooding of the reservoir to extract residual oil. In 1950s, foam flooding was proposed as a displacement system to enhance oil recovery factor. Since the 1960s, lots of experiments and field tests were introduced, and verified the effectiveness of foam flooding in enhanced oil recovery, especially for heterogeneous reservoirs.
In reservoir flooding operations, surfactants are often used to help form emulsions between an aqueous flooding solution, for example, and the hydrophobic oil—separation of the oil from rock is enhanced. Flooding with other gases or steam often also employs foam-forming surfactants—foam flooding is an enhanced oil recovery process in which foam is injected into a reservoir to improve the sweep efficiency of a driving fluid. Foam can be generated either in the reservoir pore space or at the surface before injection. Foam flooding mitigates sweep inhomogeneities such as those caused by layers with higher permeability than the surrounding formations, or those caused by gravity override.
Foam is a dispersion system formed by mixing gas, such as air, nitrogen, CO2 and so on, into liquid phase with the involvement of at least one foaming agent. In the oil industry, gas being used to generate foam is chosen from air, nitrogen, CO2, or natural gas, and liquid being used to generate foam is mainly water, such as fresh water, formation water or brine.
Foam flooding is also is being proposed as an effective way to recover tight reservoirs with extreme low permeability. One of the issues associated with recovery from these types of reservoirs is the estimation of oil recovery factor. A method of enhanced modeling or calculation of the oil recovery factor from a flooded hydrocarbon reservoir of this nature would it is believed be positively received.
There are two key limitations to current modeling methods for the estimation of oil recovery factor from a hydrocarbon reservoir. These include the actual speed of rendering of calculations, as well as the accuracy of the model. From an accuracy perspective, it is difficult to accurately estimate the oil recovery factor from a hydrocarbon reservoir subjected to foam flooding because of the need to accurately estimate sweep efficiency through the reservoir. As the permeability of the reservoir becomes lower, or the geology of the reservoir becomes more complicated, it is more difficult to come up with a proper single equation which can be used to reasonably accurately estimate oil recovery factor in such circumstances. As such, and oil recovery factor modeling method which overcame some of these limitations or rendered a more accurate result than the prior art approaches is it is believed desirable from the perspective of more accurate modeling and use of foam flooding enhanced oil recovery techniques.
One of the other limitations in current prior art approaches is the computing power required to calculate the sweep efficiency and other variables required to estimate oil recovery factor. The development of single large equations used to render oil recovery factor estimates, relying on large amounts of point data and the like from the formation of the hydrocarbon reservoir, is another limitation to the efficient use of such modeling techniques in either the planning or execution of foam flooding projects. If it was possible to come up with a revised method for the estimation of oil recovery factor in a foam flooded hydrocarbon reservoir which required less computing power or rendered quicker results than the prior art methods, it is also believed that this would positively be perceived.